Journal of Vibroengineering
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Analysis on vibration response of structure of hydrocyclone under action of internal spiral flow
Get PDFThe numerical modeling and experimental test are carried out to analyze the effects of the coupling between the structure of the hydrocyclone and the internal spiral flow on the structure motion of the hydrocyclone, and the interaction of the fluid and the structure is fully considered. The model of fluid structure interaction (FSI) of the hydrocyclone with variable diameter circular pipe is presented in this paper, and the related numerical simulation and experimental research are also carried out. Using the established fluid-structure interaction model, the dynamic characteristic of the hydrocyclone under the FSI condition is discussed, which obtained the vibration characteristics and the inter facial stress distribution characteristics. The maximum value of deformation is at the small cone-shaped part and the tail part connection of the hydrocyclone. The inter facial stress distribution is showed non symmetric state, and the maximum value of stress is located in the large cone-shaped part. After compared analysis the numerical results and the measured results, the numerical simulation is the same as the distribution trend of the test results at the maximum acceleration and position. The above analysis shows that the two-way FSI calculation model of hydrocyclone with variable diameter circular pipe is reasonable, and the motion characteristics of the structure are changed under the interaction of fluid and structure each other. The influence of the motion of the structure on the flow field of the hydrocyclone cannot be ignored. This is a problem that should be considered in the future design and application of hydrocyclone
Analysis of coupling vibration characteristics of electrically driven pile hammer linkage system
Get PDFIn order to solve the problem that electromechanical coupling had influences on the control effect of multi-pile hammers linkage, the coupling influence rules were studied. With the complex system of hammer-pile-soil being simplified, the dynamic model was constructed for the two pile hammers vibration system. The mathematical equations of systemic electromechanical coupling were established. Based on the Hamilton principle, synchronous operation conditions and system stability were established. Simulation model was developed with MATLAB/Simulink for numerical simulation. The electromechanical coupling processes and the basic system rules were obtained under different electrical motors’ speeds, the initial phase differences, soil parameters and fixing parameters. It could be found that electromechanical coupling might result in self-synchronization under given conditions. Finally, the mathematical model’s validity, theoretical derivation and simulation results were proved by some experiments. The analytical conclusions of electromechanical coupling rules provide the theoretical evidence for making control strategy on electric control linkage mode, and the basis for related engineering applications and experiments
Application of the energy finite element analysis to vibration of beams with stepped thickness and variable cross-section
Get PDFEnergy finite element analysis (EFEA) has been developed to compute the energy distribution of vibrating structures. The method adopts the energy density as the basic variable of differential equation. The energy density can be used to analyze the behavior of vibrating beams. Firstly, an EFEA equation is obtained from the classical displacement equation. In the applications of uniform and non-uniform beams, the EFEA results are compared with the analytical and FEA results. Secondly, a junction formulation solving the discontinuity problem of energy density at the junction of two beams with stepped thickness is proposed. The EFEA equation combined with junction formulation is used to solve the energy transmission problem of the coupling beams with stepped thickness and variable cross-section. The smoothed results of coupling beams are achieved, and the differences of energy density at the junctions are analyzed. The feasibility of the EFEA approach is validated by using several design examples under the various frequencies and structural damping loss factors
An improved variational mode decomposition method and its application in diesel engine fault diagnosis
Get PDFThe diesel engine is a complex mechanical device, with the characteristics of multi-source, multi moving parts, complex work. For the complex multi-component signal, it is usually necessary to decompose it into a number of single-component AM-FM signals, and each component is analyzed to extract amplitude and frequency information. VMD is essentially composed of a plurality of adaptive Wiener filter and has good noise robustness. Compared with EMD, EEMD, CEEMDAN, LMD and ITD, VMD has strong mathematical theory basis. At the same time, VMD rejects the method of recursive screening stripping. So VMD can effectively alleviate or avoid a series of problems which appear in other methods. However, it is a problem how to determine the number of decomposition layers and the penalty factor, because human factors will affect the decomposition results. In order to solve the problem, an improved adaptive genetic algorithm (IAGA) is proposed to optimize the parameters of VMD. Genetic algorithms mainly include 3 genetic operators: selection, crossover and mutation. The cross probability and mutation probability will directly affect the optimization results. In the traditional genetic algorithm, the probability of cross and mutation are fixed, and the genetic algorithm is easy to fall into the local optimal. According to the regulation of hormone regulation, the cross probability and mutation probability in evolution were improved. The permutation entropy is a new method of mutation detection, which mainly aims at the spatial characteristics of the time series itself. Therefore, the entropy of the components obtained by the VMD decomposition is used as the fitness function of the IAGA. The modal number K and penalty factor α of VMD were iteratively optimized by IAGA, and the optimal combination of parameters was obtained. Based on the proposed method, the vibration signals of the crankshaft bearing fault simulation experiment were decomposed into several components. According to the value of the permutation entropy, the fault components were selected and the energy was extracted. The fault pattern is identified by the support vector machine (SVM) successfully. The simulation analysis and the simulation experiment of the crankshaft bearing fault show that the proposed method is effective. For the diagnosis of other engines, a large number of validation experiments are needed for further research
The influence of tram tracks on car vehicle speed and noise emission at four-approach intersections located on multilane arteries in cities
Get PDFIn the article the mathematical models and results of research conducted at the intersection located on multilane artery in big city in Poland have been presented. The research allowed to describe the relationship between the speed of car vehicles and the occurrence of the tram tracks, which may be important in determining the empirical capacity of intersections located on multilane arteries in cities. This dependency may be used when updating the methods of estimation of the capacity of road intersections in Poland [1], what is the original achievement of the authors. Moreover, the results of research of noise emission in the aspect of speed change of car vehicles and the occurrence of the tram tracks have been presented. In addition, the research problem is of particular importance in the process of selecting the intersection type, which is very important during the planning and organizing traffic at intersections located in cities, where the development of the tram infrastructure is being observed
Stability of multi-hydro-turbine governing time-delay systems with sharing tailrace surge tank
Get PDFIn this paper, we focus on the stability of the hydropower plant with sharing tailrace surge tank. Considering the interaction between hydro-turbines and time-delay of hydraulic servo system, a nolinear dynamic model of multi-hydro-turbine governing time-delay systems with sharing tailrace surge tank is first established. The model can predict the transient characteristic of the hydro-turbine governing system, promoting the development of transient analysis, and safe operation of the governing system. Then, bifurcation characteristics of the system with different governor parameters and time-delays are studied. Moreover, the effect of time-delay on the stability intervals of governor parameters are investigated and its optimal value with different time-delays are obtained. All of the above analytical results can provide theoretical guidance for the actual operation of a hydropower plant with sharing tailrace surge tank
Erratum: Research on the FE and semi-analytical solution with the blade-casing rub-impact dynamical system
Get PDFSpecific damping capacity calculation of composite plates with delamination based on higher-order Zig-Zag theory
Get PDFDamping is focused in a mass of engineering applications at present. In this paper a new laminate element rests on the higher-order zig-zag theory for composite plates were presented. And then, viscoelasticity damping and frictional damping models in delaminated composites were established. The damping changes of delaminated composites with different boundary conditions were investigated via the laminate element, the effects of area and location on damping were also researched. The results revealed that viscoelasticity damping and frictional damping are in the same order of magnitude even delamination area is small, and frictional damping increase significantly when delamination area enlarged, frictional damping is needed to be considered in the damping research of delaminated composites
A novel center-tapped transformer based multilevel inverter with common DC source
Get PDFIn this paper, a novel multilevel inverter topology is proposed which uses lesser switches and anti-parallel diodes are eliminated in the circuit configuration of the multilevel inverter. Optimal switching strategy for the inverter using three different Space Vector Pulse Width Modulation (SVPWM) techniques is analyzed based on the power quality indices. The proposed model is simulated and tested using MATLAB/Simulink. Owing to the switching techniques used the harmonic content at the output of the inverter is mitigated which results in a lesser value of total harmonic distortion. Reduced number of power electronic switches results in lesser power loss. The performance of the proposed system is validated with simulation results of conventional multilevel inverters and pulse width modulation control methods. The results for various performance parameters such as efficiency, switching loss, voltage magnitude, and total harmonic distortion are analyzed
Health condition assessment of ball bearings using TOSELM
Get PDFThe health condition assessment of Electric Multiple Unit (EMU) traction motor ball bearing is one of the key issues of high-speed train running safety. In order to assess health condition of EMU traction motor ball bearing, an online-sequential extreme learning machine algorithm based on TensorFlow (TOSELM) is proposed. Samples data set is divided into normal condition and fault condition using vibration data of ball bearings. This paper uses health condition accuracy rate index to evaluate TOSELM algorithm performance. The proposed approach is verified by public data set and private data set. The experiment results show the proposed method is an effective method for ball bearing health status assessment